The limited availability of appropriate animal models for bipolar disorder (BPD) is repeatedly mentioned as one critical factor hindering research of its underlying biology as well as the ability to develop new treatments. As part of the molecular revolution in psychiatry, there is a growing emphasis on development of animal models through targeted gene mutations. Indeed, mutation based models provide promise but have their own shortcomings and need to be combined with additional approaches. Some of these additional strategies include attempts to develop better tests to evaluate BPD-like behaviors in animals, identification of models for disease endophenotypes, and the utilization of comparative biology approaches to explore model animals based on strains comparison or nontraditional animal species with a biology that is more relevant to the disorder. Combining strategies and enhancing strong collaborations between clinicians, animal behavior scientists, animal physiologists and molecular scientists might be the best way to achieve predictive and etiologically valid models.
We have recently reported an animal model of schizophrenia with gene-environment interaction by inducing immune activation during perinatal period in transgenic mice with human dominant-negative form of disrupted-in-schizophrenia 1 (DN-DISC1). In the present study, we investigated the effects of antipsychotics on the behavioral deficits in this animal model. From postnatal day 2 to 6, neonatal DN-DISC1 mice were repeatedly injected polyI:C. An atypical antipsychotic clozapine or a typical antipsychotic haloperidol was administered orally once a day for 7 consecutive days before the start of the series of behavioral tests. Memory impairment in polyI:C-treated DN-DISC1 mice was ameliorated by administration of clozapine but not haloperidol. Both antipsychotics suppressed the potentiation of MK-801-induced hyperactivity although they had no effect on deficit of social interaction in polyI:C-treated DN-DISC1 mice. These results suggest that polyI:C-treated DN-DISC1 mice may be useful in evaluating the effects of antipsychotics.
Hyperacusis, a marked intolerance to ordinary environmental sound, is a common symptom associated with a variety of neurological diseases. Although severe hyperacusis can significantly degrade the quality of life, the mechanisms that give rise to hyperacusis are poorly understood. In this study, we examined the relationship between a hyperacusis-like behavior, specifically an enhanced startle reflex amplitude, and neural hyperactivity in auditory cortex (AC) which occurred after acoustic overstimulation or high-dose salicylate treatment. Bilateral noise exposure (120 dB SPL, narrow band noise, 12 kHz, 1 h) significantly enhanced startle reflex amplitude 1 day post-exposure, indicative of hyperacusis. The firing rates of AC neurons also increased after the noise exposure consistent with previous reports. Local or systemic salicylate treatment also significantly increased sound-evoked AC neural activity and significantly enhanced the amplitude of the startle reflex, a behavioral manifestation of increased loudness and neural gain. S-baclofen and R-baclofen, GABA-B receptor agonists, strongly suppressed the AC firing rates and sound-evoked local field potentials and reduced the salicylate-induced enhancement of AC firing rate. Importantly, S-baclofen also reduced the exaggerated startle reflex response induced by noise exposure and salicylate. Collectively, these results suggest that noise and salicylate induced hearing loss reduced cortical inhibition which in turn leads to enhanced AC responses and hyperacusis-like behavior. Our results suggest that increasing GABA-medicated inhibition with baclofen reduces AC central gain and reverses the exaggerated neural and behavioral responses evoked by noise exposure and high doses of salicylate (Supported by NIH, RNID and AFAR).
Medrano, W. A. ; Calzavara, M. B. ,; Levin, R. ; Frussa-Filho, R. ; Ablio, V.C. ,
Department of Pharmacology, Federal University of Sao Paulo
Laboratrio Interdisciplinar de Neurocincias Clnicas LiNC, Department of Psychiatry, Federal University of Sao Paulo
Recently, we have described that spontaneously hypertensive rats (SHR) present a contextual fear conditioning (CFC) deficit that is specifically reverted by antipsychotics and potentiated by proschizophrenia manipulations. Based on these findings, we suggested that this could be a useful animal model to study abnormalities in emotional processing in schizophrenia. The aim of this work was to investigate the role of basolateral amygdala, prefrontal cortex and nucleus accumbens in the CFC deficit presented by this strain. These structures were chosen because they are related both to emotional processing and schizophrenia. For this purpose, tetrodoxine and veratridine (that inactivates and activates neuronal functioning, respectively) were injected in these structures previous to the acquisition of the CFC. Inactivation of nucleus accumbens as well as activation of prefrontal cortex attenuated the deficit presented by SHR. These results are in accordance with the proposed overactivity of the mesolimbic system and hypoactivity of prefrontal cortex that underlie the pathophysiology of schizophrenia. In this context, they reinforce the intersections between CFC deficit in SHR and emotional processing abnormalities in schizophrenia.
Nolen and Hoy (1984) determined that a spike rate of 220 Hz averaged over 100 ms in the AN2 interneuron elicits avoidance steering to ultrasonic stimuli in female Teleogryllus oceanicus,. Recent studies however, suggest that instantaneous rather than averaged spike activity is a more realistic predictor of how neural circuits operate. Also, bats sympatric with this Australian cricket never produce echolocation calls of 100 ms. We examined the instantaneous spike rates (ISRs) of AN2 responses corresponding to the threshold spike train response reported by Nolen and Hoy (1984) to elicit avoidance steering (behavioural threshold (BT)) within the first 10 ms (i.e., a typical natural duration of echolocation calls) and 33 ms (i.e., the minimum latency between the first AN2 spike and muscle activation) by generating AN2 neural response traces using the same stimulus criteria as used by Nolen and Hoy (1984). Our re-estimation of these responses shows that the ISR at BT approaches 450 Hz for the first four spikes (defined as bursting), which reduces to less than 220 Hz after 13 spikes. When relating AN2 spike responses to the natural echolocation call durations of sympatric bats we suggest that avoidance steering in T. oceanicus may be elicited by bursting followed by a spike train firing at sufficiently high rates with lower duration calls requiring greater intensity to produce such a response.
The behavioral effects of different prenatal stress (PNS) schedules were examined together with genetic predisposition, in male and female prepubertal depressive- and anxious-like Wistar Kyoto (WKY) and control Wistar rats. Groups: PS: Daily 1hr maternal restraint stress (gestational days 1420), RPS: 7-days of Random schedule restraint throughout pregnancy; Control: undisturbed. Offspring were tested on postnatal days 29-35 for exploration and novelty approach (or "anxiety-like" profiles), social play, swim-test immobility ("depressive-like" behavior) and corticosterone (CORT) levels (basal & post-stress). Results PNS induced an increase in anxiety-like behaviors in WKY, particularly in females, and decreased them among Wistar males compared to unstressed controls. On the other hand, PNS reduced immobility in the swim test and increased diving in WKY compared to control in both sexes. Within the Wistar strain there was only a minor effect in the swim test. Post stress CORT levels were elevated in WKY compared to Wistar and in males compared to females. Basal CORT levels in the PS group were lower than controls. PNS-Wistar performed more pinning, rearing and climbing the cage-cover than controls in a social interaction test, while WKY remained unaffected. Overall, RPS decreased Wistar and increased WKY body weight compared to controls. Thus, while prenatal stress induced opposite-direction effects within the WKY strain, its effects on the "normal control" Wistar strain exposed social hyperactivity and risk-taking behaviors. The results of the present study support the importance of the environment during gestation on long term anxiety and depressive like behaviors in the offspring.
Support: Israel Science Foundation.
Phan, A.1; Gabor, C.S.2; MacLusky, N.J.2; Choleris, E.1
1Dept of Psychology, 2Biomedical Sciences, University of Guelph.
Estrogens effects on learning and memory are typically studied hours to days after their administration when transcriptional responses predominate. In addition to these genomic effects, estrogens also have very rapid effects on neuronal electrophysiology and morphology, which occur within minutes to an hour of estrogen application. 17b-estradiol application to hippocampal tissue was reported to enhance long-term potentiation and glutamate depolarization within minutes, suggesting that it may act in a rapid fashion to improve learning and memory. Rapid estrogen effects on neuronal electrophysiology, morphology, as well as other behaviours tend to be reported at drug doses much higher than needed for their genomic effects. Thus, there is concern as to whether these rapid estradiol effects are physiologically relevant. Therefore, we determined whether a physiological dose of 17b-estradiol can rapidly affect spatial learning, a type of learning that is hippocampus dependent. Young adult, ovariectomized, female CD1 mice were injected subcutaneously with vehicle, 1.5mg/kg, 2mg/kg, or 3mg/kg of 17b-estradiol, 15min prior to testing in an object placement paradigm. This paradigm was completed within 40min of drug injections and the results were ethologically analyzed. We found that administration of 2mg/kg of 17b-estradiol improved object placement learning in these female mice within the rapid 40min time frame. This dose of 17b-estradiol has been shown to produce physiological levels of plasma estradiol in rats. Therefore, 17b-estradiol can rapidly improve object placement learning, and these rapid effects can occur within the physiological range of estradiol levels. Funded by NSERC.
Massimiliano Di Filippo, MD and Paolo Calabresi, MD
Clinica Neurologica, Università di Perugia, Perugia, Italy and IRCSS Fondazione S Lucia, Rome, Italy
The striatum is the major division of the basal ganglia, representing the input station of the circuit and arguably the principal site within the basal ganglia where information processing occurs. Striatal activity critically control motor function and learning and many parts of the striatum are also involved in reward processing and cognitive functions. The crucial role played by the striatum in learning and cognitive processes is thought to be based on changes in neuronal activity when specific behavioral tasks are being learned. Accordingly, excitatory corticostriatal synapses onto both striatal projecting spiny neurons and interneurons are able to undergo the main forms of synaptic plasticity, including long-term potentiation (LTP), long-term depression (LTD), short-term forms of intrinsic plasticity and spike timing-dependent plasticity. Striatal LTP and LTD, the two main forms of synaptic plasticity, strongly depend on the activation of dopamine receptors. LTD is thought to be initiated postsynaptically but expressed through a presynaptic reduction in neurotransmitter release and it requires dopamine D2 receptors, group I mGluRs, L-type calcium channels, and CB1 receptor activation, but notably, not NMDA receptors. Conversely, LTP at glutamatergic synapses onto striatal medium spiny neurons involves activation of NMDA-type glutamate receptors and D1 dopamine receptors. In physiological conditions striatal neuroplasticity is thought to allow the short-term and long-term selection and differential amplification of cortical neural signals modulating the processes of motor and behavioral selection within the basal ganglia neural circuit. Following pathological insults and in different experimental models of neurological diseases such as basal ganglia neurodegenerative disorders, stroke and epilepsy, striatal synaptic plasticity has found to be altered suggesting that, at least in part, plastic abnormalities at striatal synapses may underlie symptoms onset and/or disease progression in human pathological conditions.
Postpartum depression affects 15% of new mothers and previous experience of depressive episodes increases the risk for postpartum depression. To better understand the causes and progress of this common affective disorder we examined a corticosterone (CORT)-induced rodent model of postpartum depression. In the present study, we aimed to investigate the effects of CORT treatment in the dams first postpartum period on maternal mood after a subsequent pregnancy. Sprague-Dawley female rats received either sesame oil (control) or CORT (40 mg/kg) injections for 23 days during their first postpartum period. The dams were observed for "depressive-like" behaviour on the Forced-Swim Test (FST) from postpartum day 21-22. Following a second pregnancy, dams were again tested on the FST apparatus at postpartum day 4 and 21. During the first postpartum period, CORT-treated dams displayed an increase in immobility in the FST compared to oil controls, indicative of "depressive-like" behaviour. However, the effect was reversed in the second postpartum period with the CORT dams showing less immobility than control dams in the FST. Interestingly, control dams had an increase in time spent immobile during second postpartum period compared to first. This implied that the conditions of the first motherhood have a substantial influence on the second postpartum period; in particular, it hinted that the CORT dams may had a dampened stress response. Further investigations are necessary to fully understand the effect of parity on postpartum depression.
Phan, A.1; Pfaff, D.2; Choleris, E.1; Kow, L-M.2
1Dept of Psychology, University of Guelph, ON. 2Laboratory of Neurobiology and Behavior, The Rockefeller University, NY.
Histamine induces excitatory responses in the ventromedial hypothalamic nucleus (VMN), potentially modulating VMN dependent behaviors (e.g., sexual behaviors). Rapid (minutes) application of 17b-estradiol to the VMN potentiates histamine-induced membrane depolarizations. Thus histamine and estrogens may interact to influence sexual arousal. The rapid effects of estrogens on neurons can be mediated through both estrogen receptor (ER)a and ERb, although behavioral studies indicate that ERa is more important than ERb in mediating sexual behaviors. Therefore we used selective ER agonists PPT (ERa) and DPN (ERb) to investigate whether estradiols effects on histamine-induced depolarizations were mediated by either or both subtypes. Whole cell patch-clamp was performed on VMN neurons from female Sprague-Dawley rats, 11-25 days old. Membrane potentials were recorded as a picospritzer delivered histamine (10mM in ejecting pipette) at 5min intervals before, during and after 5-15min of PPT (100nM) or DPN (100nM) bath application. PPT replicated the findings of 17b-estradiol, potentiating histamine-induced depolarizations in 8/9neurons. However, DPN had a range of effects, potentiating (3/12neurons), attenuating (2/12neurons) or having no effect (7/12neurons) on histamine-induced depolarizations. These effects of DPN are not likely due to random variation in the recordings. When both DPN and PPT were applied to the same neurons in 2 instances, DPN had no effect or attenuated the response, while PPT potentiated the histamine depolarizations. Therefore, the rapid effects of 17b-estradiol on histamine depolarizations in the VMN appear to be mediated through ERa. While ERb is also capable of rapidly influencing histamine depolarizations, the functional significance of this is not clear. NIH and ERA funded.